Control mechanism



8, 1967 H. B. KAST 3,334,521

CONTROL MECHANISM Original Filed Oct. 1, 1965 2 Sheets-Sheet 1 FM m J)24 M zz INVENTOR.

" yak/4:0 5 M07 Irina/e1- Aug. 8, 1967 H. B. KAST 3,334,521

' CONTROL MECHANISM Original Filed Oct. 1, 1965 2 Sheets-$heet INVENTOR.34 wlwea 5 m5;

WC W4- United States Patent 3,334,521 CONTROL MECHANISM Howard B. Kast,Fairfield, Ohio, assignor to General Electric Company, a corporation ofNew York Continuation of application Ser. No. 495,763, Oct. 1, 1965.This application May 27, 1966, Ser. No. 553,578 5 Claims. (Cl. 74-110)This invention relates to a control mechanism and, more specifically, toa control mechanism which allows an actuator to move a load from one ofa plurality of pre-selected stop positions to another such stopposition, yet prevents the load forces acting upon the mechanism fromthemselves actuating the mechanism away from any pre-selected stopposition. This application is a continuation-impart of application-SenNo. 248,534, filed Dec. 31, 1962, now abandoned.

In the design of aircraft and, in particular, aircraft engine accessoryand control systems, one of the most pressing problems facing thedesigner is how to ensure that the system components will perform in themanner and at the time required. A facet of this problem concerns theneed for built-in safeguards to make certain a given system or accessorywill be energized when-and only whenthe operator desires it to performthe assigned task. One particular area where these safeguards are veryimportant is in the design of systems for multi'engine jet aircraft.

Until very recently operation of single and multiengine jet aircraft,with the possible exception of a few experimental military vehicles, haslargely been confined to flight speeds of Mach 2.0 (about 12/00 mph.)and under. More advanced high-Mach military aircraft and supersoniccommercial jet transports scheduled for use in the near future will,however, operate at considerably higher speeds. It has therefore becomenecessary to place added stress on reliability of the aircraft engines,accessories and related control systems. The related problems ofreliability and safety will perhaps be more acute in the case of futurehigh-Mach aircraft utilizing advanced high performance turbojet typeengines. For reasons of passenger and crew member safety and missionaccomplishment, it will therefore be essential that such an aircraft beable to continue to perform its flight mission with -oneor perhapsmoreof its engines non-operative.

It is, of course, obvious that a certain point can be reached in anymulti-engine installation when enough of the powerplants would becomenon-operative to prevent the continuation of flight. Assuming, however,that flight is still possible, one of the primary problems in thesemulti-engine high speed aircraft utilizing turbojet or turbofan engines,i.e., any engine which has rotating components such as compressor orpower turbine bladed rotors mounted on .a shaft, concerns the highrotative speed of the shaft caused by the force of the air entering theengine inlet. To explain, if a gas turbine engine becomes non-operativeat a high Mach number, for example, because of failure of any of themany accessory, fuel system, or lubrication system components, thesupersonic velocity of the air produces an extremely high total pressureat the inlet of the engine, which will be combined with a low totalpressure at the exit. When the high rotative speed of the non-operatingengine, involving extremely large moments of rotating inertia, iscoupled with a dearth of engine lubrication system heat sink (sincethere would no longer be fuel flowing to the nonoper-ating engine andthe heat sink or cooling medium for the lubrication fluid normallyfurnished by the fuel in such aircraft would not be available),inevitably the result is seizure of the rotor shaft bearings. An abruptseizure could produce "an undesirable and even dangerous condition inthe aircraft or vehicle by reason of the engine mounting structure orengine nacelle suffering severe structural damage during the sudden andviolent deceleration of the rotating components. In the case of asupersonic commercial transport, or even a military bomber, it will bevital that the aircraft continue to main tain altitude and speed usingthe remaining operating engines. That the problem is particularly acutein aircraft designed to fly at Mach 2.5 and above will be realized whenit is understood that if the fuel supply is cut off, for example, aturbojet engine can windmill at up to 93% of full speed. The situationis further complicated by the fact that in the design of aircraftcapable of these high speeds, the problem of weight is critical. Thus,it has been found that proposals for use of inlet duct closure means,such as flaps, or compressor variable inlet guide vanes have had to beabandoned as impractical since these structures, of necessity, must berelatively massive and heavy to withstand the extreme air blast. Anothersuggested solution involving reverse turbine rotor blade rairimpingement during windmilling to brake the rotor shaft has also provedto be less than desirable due to the inefliciency occasioned by theunfavorable curvature of the typical turbine blade airfoil. It willtherefore be clear that in any means or system adopted to controlturbojet engine windmilling, reliability and safety of operation areimportant factors.

There are, in addition, numerous other commercial and industrialmachines wherein reliability and safety of operation will be primedesign criteria. Specific-ally, where actuation means are necessary tomove a control mechanism between pre-selected operating positions, orfrom an operating to a non-operating position-and vice versa--it will behighly desirable to provide means to ensure that forces imposed on themechanism through the load (aerodynamic forces, for example, in aturbojet engine application) do not themselves actuate the mechanism.

Accordingly, a general object of the present invention is to provide animproved control mechanism having a positive latching means for use inan operating environment requiring a high degree of safe operation.

A more specific object of the present invention is to provide a safe,reliable, positive latching means in a control mechanism adapted to movea member between pre-selected operating positions, or from an operatingto a non-operating position-and vice versawherein it will be assuredthat forces acting on the mechanism by reason of loads imposed on themember which the mechanism operates do not in and of themselves resultin opera tion of the mechanism.

Briefly stated, one embodiment of my invention comprises in. a controlsystem for use in a high reliability/ safety environment such as, forexample, a high-speed aircraft having a multiplicity of turbojet typeengines each including a compressor having a row of adjustable statorvanes adjacent the compressor outlet, a plurality of lever arms aflixedto the row of stator vanes, a power source, and motor means energized bythe power source, a control mechanism connecting the motor means withthe stator vanes through the plurality of lever arms. The controlmechanism includes a bellcrauk and a member adapted to be driven along apath between two extreme positions, the member moving relative to therow of stator vanes when so driven and carrying with it the bellcrankpivotally mounted on the driven member at the juncture of the bellcrankarms. Latching means freely mounted at the end of one of the arms of thebellcrank extends transversely thereof so as to engage an elongated slotin a support member fixedly located with respect to the driven member.The slot is angled with respect to said path and the latching means isguided therealong in order that as the driven member moves along saidpath towards either of the said extreme positions-said path by the motormeans being connected to the other arm of the bellcrankthe latchingmeans is caused to engage a short arcuate slot at either end of theangled slot when the driven member reaches a respective one of either ofsaid positions. The latching means is stopped in either arcuate slot andretained therein against the impoistion of external forces imposed onthe driven member, e.g., through the vanes, but is immediatelyreleasable ifand only ifthe motor means is actuated to move the drivenmembers along the path towards the other of the two extreme positions.This feature is provided by reason of a particular relationship of thecircular axes of the armate slots and the bellcrank pivot axis. That is,a first one of the slots has its circular axis co-linear with the axisof the bellcrank pivot when the driven member is in one of said extremepositions and, conversely, the other slot has its axis co-linear withthe bellcrank pivot axis when the driven member has moved along saidpath to the other of said extreme positions.

Other applications, objects, and advantages of the invention will becomemore apparent and the invention better understood when the followingdetailed description of the described embodiment is read in conjunctionwith the drawings thereof wherein:

FIG. 1 is a side view of a typical turbojet aircraft engine, partiallycut away to show the arrangement of the components thereof, the enginehaving a row of adjustable stator vanes;

FIGS. 2 and 3 are enlarged fragmentary views partially in cross-section,of a portion of the means used to rotate a stator vane about its axis,and indicating vane position in both a normal operating (open) positionand a nonoperative (closed) position;

FIG. 4 is a schematic drawing showing the components of the describedcontrol system including positive latching means for locking theactuating means in the pre-selected stop positions;

FIG. 5 is an enlarged view of the latching means of the system in one(e.g., open) position; and

FIG. 6 is an enlarged view of the latching means of FIG. 5 in another(e.g., closed) position; and

FIG. 7 is a view along line 77 of FIG. 5.

While the subsequent detailed description of the control mechanism showsthe use of such in a windmill brake control system for a conventionalsingle shaft turbojet engine in a multi-engine installation, it will beunderstood that other apparatus in addition to gas turbine engineshaving one or more compressor and turbine rotors mounted on a main shaftmay equally benefit from the teachings of the invention such as, forexample, a motor or engine control or accessory system wheerin positivecontrol of movement of movable mechanism components is desired. Thus,the device is not limited to the aircraft field but is applicablewherever actuators, including hydraulic, pneumatic or screwjack types,are used.

Turning now specifically to FIGURE 1, shown is a typical turbojet enginehaving an inlet end, indicated generally at 10. The engine includes acompressor rotor 12 mounted on a central shaft 14. The shaft 14 alsosupports a turbine rotor 16 furnishing the driving force for thecompressor rotor. The turbine rotor may be single or double staged (dualrotors), as shown. Intermediate the compressor and turbine rotors aremeans for providing combustion in the engine, such as a plurality ofliners or cans, one of which is indicated at 18. The engine componentsare surrounded in the usual manner by an outer casing 20 providing aduct through which air flows in the direction of the large arrow inFIGURE 1. After combustion takes place, the hot gas stream exits throughan engine exhaust nozzle, indicated generally at 22. One portion of theactuating mechanism for the engine depicted, which will be one of anumber of like engines and partial systems in a multi-engineinstallation, comprises the row of variable stator vanes 24 located atthe rear of the compressor. The stator vanes, as is normal, arepositioned adjacent a row of compressor rotor blades, indicated at 26.As shown in the enlarged view of FIG- URES 2 and 3, each variable statorvane 24 includes a trunnion 28 projecting outwardly through an opening30 in the casing 20. Secured to the threaded outer end of the trunnionby a nut 31 is a lever arm 32, the other end of which is connected bysuitable means, such as pin 34, to a circumferentially-extendingactuator ring 36. The ring is adapted to be moved in a rotary directionwith respect to the engine and preferably comprises a pair of so-calledhalf-rings suitably joined. For a more complete description of thevariable stator engine system, reference may be made to the followingpatents of common assignment: Neumann No. 2,933,234; Eckenfels et al.No. 2,842,305; or Warren No. 2,999,630.

The primary elements of the control system power supply used in thedescribed jet engine windmill brake arrangement are schematicallydepicted in FIGURE 4. The system is hydraulic in the case and includes asupply of hydraulic fluid contained in a tank 38 suitably affixed to theengine casing, a pump 40 which projects fluid from the tank throughconduits or connecting lines 41 and 42 intermediate the pump tank, and avalve means 44. The valve means 44 is preferably electrically controlledby a pilot control 46 situated in the aircraft cockpit and operablyconnected by lines 47 and 48 to the valve means. In response to a signalfrom the pilot the valve operates in a known manner to supply fluidthrough conduits 49 and 50 to actuator or motor means, indicatedgenerally at 51.

Turning now to FIGURES 5-7, illustrated in detail is the controlmechanism and latching means, indicated generally at 52, of the subjectinvention, which in the disclosed control system provides movement ofthe stator wanes against the aerodynamic loads between the normaloperating (stator vanes open) and the emergency nonoperating (statorvanes closed) positions, shown in FIG- URE 3, the latter being used forwindmill braking. In the disclosed embodiment, the hydraulic actuator 51includes an internal piston 53 drivingly connected to one end of apiston rod 54 movable back and forth (up and down in the drawing) inresponse to increasing or decreasing fluid pressure in lines 495tlleading to opposite sides of the piston. The other end of the rod 54 ispivotally connected at 56 to one arm of a bellcrank, indicated generallyat 58. The arm 60 to which the rod is connected is the shorter arm ofthe bellcrank with the other arm 61 being considerably longer and beingarranged to extend generally in the same direction as the piston rod 54.Thus, the arms extend at right angles to each other. The bellcrankitself is pivotally supported at 62at the junction of arms 60 and 61by aclevis 63 aflixed to the vane actuator ring 36. The free end of arm 61supports a pin member 64 disposed in a bearing 65. The bearing islocated in a hole 67 in a boss 68 at the extremity of the arm. As shownperhaps more clearly in FIGURE 7, the pin 64 projects considerably onboth sides of the boss with its axis being generally perpendicular tothat of the arm 61, as is the axis of the bellcrank pivot pin 62. Meansfor guiding and directing movement of the latching pin 64 and, hence,movement of the bellcrank to control the position of the stator vanes,is provided in the form of a bracket or stop plate, indicated generallyat 70. The bracket or plate, as seen in the plan vieW of FIGURES 5 and6, is rectangular and includes a cam track, generally indicated at 72.The cam track may be described as somewhat Z-shaped, including anelongated intermediate portion 73 and two shorter end portions 7475. Itwill be noted that the end portions form arcuate segments ofapproximately equal length and radius. As seen in FIG- URE 7, the camtrack is preferably double, being located in upper and lower platformportions 77 and 78, respectively, of bracket 72. The double platformarrangement, while not absolutely necessary, acts to prevent anytendency for the rotating latch pin 64 to bind as it moves within thetrack. In addition, collars 79-79 are used to fix the pin axially in thebearing 65, while permitting it to rotate about its axis. A pair ofresilient gripping means, such as clips 8080, are aflixed at 8181 to theouter surface of platform portion 77. The clips, while not arequirement, aid in maintaining the pin at either of the stop locationsformed by the arcuate segments 74- 75 of the Z-shaped cam track.Finally, the double platformed bracket 70 is itself aflixed to theengine casing by permanent fastening means such as rivets 8282, passingthrough a bent-over flange portion 84 of the bracket.

In operation, assume that all the engines of FIGURE 1 in themulti-engine jet propelled aircraft installation are operating normally.In such case, the stator vanes 24 will be in the normal operatingposition shown in FIGURE 3, whereby passages 86 are provided betweenadjacent vanes to permit the flow of air through the compressor. In thiscase, the control system stator vane actuating mechanism, in particularthe pin or latching member 64 is in the position shown in FIGURE 5, thatis, in the clip 80 in the arcuate segment 74 at one of the extreme endsof the intermediate portion 73 of cam track 72. The pin will be lockedin this position and thus will lock the vanes in the desired positionsince aerodynamic loads transmitted from the vanes to the bellcrank 58,through ring 36 and clevis 63, create forces which are permitted to actthrough the center of the bellcrank pivot pin 62 only. That is, when themember 36, has been moved to the upper one (in the drawing) of the twoextreme positions of movement along its driven path, which, of course,moves the bellcrank and latching pin 64 as shown, the axis of theprojected circle of the arc of stop means 74 is co-linear with the axisof the pivot pin 62. Thus, the center of the pin and the are indicatedon the drawing are identical. This results in no turning moment aboutthis pivot point and hence no force transmission to the actuator throughthe shorter arm 60. This is true regardless of whether the load force isup or down (in the drawing). The clip 80 is useful in cases whereunusual vibratory loads may be expected, but in most applications thedisclosed arrangement of the common bellcrank pivot point and arcuatestop means axis location will be suflicient to positively lock the pinin position.

Next, assume a sudden emergency requiring shutdown of one of theengines. The aircraft operator will immediately energize the pilotcontrol 46 which will operate the valve means, increasing the supply offluid to line 49, while at the same time decreasing, or venting, thefluid in line 50. The resulting differential pressure change acrosspiston 53 causes a downward stroke of 54 which creates a clockwisemoment about pivot point 62 through the shorter arm 60 of the bellcrank.This will unlatch the mechanism by carrying the pin member 64 to move tothe right (in the drawing) along the arc of the segment 74 and into theintermediate portion 73 of the cam track. The pin follows the cam trackalong the downward stroke until it reaches the extreme left-hand portionof curved segment 75. Since the moment about point 62 is stillclockwise, the pin will immediately move along the arc of the lowerradius until it engages the bottom (in the drawing) spring clip 80. Thisstops movement of the actuator and, hence, the stator vanes, the latterbeing now in the closed or compressor blocking position shown in FIGURE3, i.e., with passage 86 closed by reason of the trailing and leadingedges of adjacent vanes being in abutment. Again, aerodynamic loadforces applied to the actuation system through ring 36 cannot move thebellcrank either up or down, for the same reason as explained 'above.That is, as shown in FIG. 6, the axis of pin 62 and the axis of theprojected circle of segment 75 are co-line-ar, the axis of arcuatesegment 74 remaining, naturally, as before. Thus, in the other of thetwo extreme positions of movement of the driven member, i.e., at thebottom in the drawings, forces external to the system cannot unlatch orunlock the mechanism.

If it should then be desired to move the stator vanes from the blockingposition in this case, or to move in a another aircraft applicationmovable members, such as,

for example, the exhaust nozzle flaps shown in the patent toSchaefer-2,969,641-or the blocker-doors in the thrust reversing meansdisclosed in Nash-3,024,605, both of common assignment, unlatching isaccomplished by energizing the actuator 51 in the opposite direction tothat last mentioned. In other words, fluid pressure is supplied to line50, as shown in FIGURE 6, as line 49 is vented, causing an upward strokeof rod 54 and a counterclockwise moment about pivot point 62. This willunlatch the pin members 64 from the stop segment 75 and move the load(ring 36) towards the upper stop means or segment 74.

The disclosed invention therefore provides a control system having anovel, simple and highly reliable positive latching mechanism useful inlocking a movable load in a machine between two extreme pre-selectedoperating positions, or between a pro-selected operating andnonoperating position. While described in combination with amulti-engine aircraft windmill brake system, it is understood that suchother uses for the control system and latching mechanism as will bewithin the skill of the art are intended to be within the scope of theappended claims.

1. Control mechanism comprising,

an actuator having a reciprocable output rod,

a member to be driven by said actuator,

a bell crank pivotally mounted on said member,

said output rod being pivotally connected to a first arm of said bellcrank and exerting atorque force thereon in a given direction, arelatively fixed member having a cam surface angled relative to the pathof travel of said output rod, said bell crank having a second arm with afollower engageable with said cam surface whereby movement of saidoutput rod in one direction will be transmitted to said driven member asthe bell crank pivots thereon in a given direction,

said fixed member having a socket, extending generally in the givendirection of the torque force of the bell crank,

whereby said follower will be automatically displaced into said socketby said actuator, thereby latching the driven member in one extreme ofmovement.

2. Control mechanism as in claim 1 wherein,

the member to be driven is guided for movement in a plane parallel tothe path of movement of said output rod,

the arms of said bell crank are substantially apart,

and

the first arm is generally normal to the path of movement of said outputrod.

3. Control mechanism as in claim 2 wherein,

said socket is formed radially of the pivot center of the bell crank insaid one extreme of movement, and

said first bell crank arm is substantially shorter than the second bellcrank arm.

4. A drive system as in claim 1 wherein,

spring detent means are provided for releasably retaining said followerin said socket.

5. Control mechanism as in claim 2 wherein,

said fixed member has a generally Z-shaped slot receiving said follower,

said slot providing said cam surface and socket and also providing asecond cam surface and second slot for transmitting motion to the drivenmember upon movement of the output rod in the opposite direction andlatching the driven member in an opposite extreme position.

(References on following page) References Cited UNITED STATES PATENTSJohnston 74107 Brown 74107 Capra 74-53 Bouillon 74-53 Phelan 74527Walker 253-78 8 3,045,500 7/1962 Bruun 74--110 3,083,892 4/1963 Carey eta1. 230-114 FOREIGN PATENTS 5 900,624 12/ 1953 Germany.

FRED C. MATTERN, JR., Primary Examiner.

W. S. RATLIFF, Assistant Examiner.

1. CONTROL MECHANISM COMPRISING, AN ACTUATOR HAVING A RECIPROCABLE OUPUTROD, A MEMBER TO BE DRIVEN BY SAID ACTUATOR, A BELL CRANK PIVOTALLYMOUNTED ON SAID MEMBER, SAID OUTPUT ROD BEING PIVOTALLY CONNECTED TO AFIRST ARM OF SAID BELL CRANK AND EXERTING A TORQUE FORCE THEREON IN AGIVEN DIRECTION, A RELATIVELY FIXED MEMBER HAVING A CAM SURFACE ANGLEDRELATIVE TO THE PATH OF TRAVEL OF SAID OUTPUT ROD, SAID BELL CRANKHAVING A SECOND ARM WITH A FOLLOWER ENGAGEABLE WITH SAID CAM SURFACEWHEREBY MOVEMENT OF SAID OUTPUT ROD IN ONE DIRECTION WILL BE TRANSMITTEDTO SAID DRIVEN MEMBER AS THE CRANK PIVOTS THEREON IN A GIVEN DIRECTION,SAID FIXED MEMBER HAVING A SOCKET, EXTENDING GENERALLY IN THE GIVENDIRECTION OF THE TORQUE FORCE OF THE BELL CRANK, WHEREBY SAID FOLLOWERWILL BE AUTOMATICALLY DISPLACED INTO SAID SOCKET BY SAID ACTUATOR,THEREBY LATCHING THE DRIVEN MEMBER IN ONE EXTREME OF MOVEMENT.